#include<bits/stdc++.h>
#define ONLINE_JUDGE
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 110, INF = 0x3f3f3f3f;

int n;
string s;
set<char> a, A;

void solve()
{
    cin >> n >> s;
    for (int i = 0;i < s.length();i++) {
        if (s[i] >= 'a' && s[i] <= 'z') a.insert(s[i]);
        else A.insert(s[i]);
    }
    int flag = 1;
    for (int i = 0;i < 26;i++) {
        if (a.count(i + 'a') != A.count(i + 'A')) { flag = 0;break; }
    }
    if (flag) cout << "YES";
    else cout << "NO";
}

signed main()
{
    // ios::sync_with_stdio(0);
    // cin.tie(0);cout.tie(0);
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    //cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}